1. Technical Field
The present invention relates to a hydrodynamic bearing spindle motor that is installed in a device for recording and reproducing information to and from a disk-shaped medium such as a hard disk drive (hereinafter referred to as HDD).
The present invention relates to a spindle motor for a HDD or the like in applications in which there is the possibility of a large swinging vibration being imparted, such as in mobile applications, and more particularly relates to technology for suppressing the generation of noise during swinging and suppressing an increase in current consumption in a spindle motor for a thin, small-diameter HDD.
2. Description of the Related Art
HDDs in which a hydrodynamic bearing spindle motor is installed have come to be widely used not only in notebook PCs, but also in digital audio players and so forth. A major prerequisite of a HDD used for mobile applications is that it be thin, and on top of this, it is particularly important that the device operate at low current consumption, and have dramatically suppressed disk vibration if subjected to disturbance vibration or the like. Many proposals have been made in an effort to satisfy these requirements.
For example, a structure has been proposed in which a large-diameter thrust bearing is constituted between the sleeve of the bearing and the hub on which the disk is mounted (see, for example, Japanese Laid-Open Patent Application 2005-045924). A structure has also been proposed in which the outer peripheral cylinder part of a large-diameter flat shaft is used as a radial bearing, and a thrust bearing is constituted at the upper and lower ends thereof (see, for example, Japanese Laid-Open Patent Application 2001-124065).
Furthermore, it has been proposed that a large-diameter flange be provided to the distal end of a shaft, so that when a disturbance moment is imparted, the load will be borne by both the radial bearing and the thrust flange, which increases the stiffness of the system as a whole (see, for example, Japanese Laid-Open Patent Application 2002-171719).